Car Problems: High Fuel Use, Weak Acceleration?

Hello fellow diesel mechanics.


Golf IV, ALH engine - 90 horsepower, 1999, 101,000 km.

I'm completely freaking out. Recently, my oil burner has been consuming 0.5-0.8 liters more than before. Also, the car feels like it's driving on chewing gum.
Previously, 4.8-5.1 liters per 100 kilometers.
'Minor issues like diesel filters, different tires, the air conditioning system, a stiff-feeling loader adjustment, and chewed-on pneumatic lines for the loader or EGR control system have already been checked and are in order. There is also no visible black or blue smoke. Oil consumption is approximately 0.5 liters per 10,000 km.'
There are no error codes stored in the system. I've also experienced the issues with the loss of power around 3000 RPM and the poor cold start. The maximum speed is being reached, although it takes a while to get there.


But where and how is the best way to search?
My friendly (but also equally rude and incompetent) mechanic had dollar signs in his eyes when I came in to have the error codes read.

Unfortunately, I don't have a VAG.COM interface, and I'm unable to proceed further with the tools I have available.

My suspicion is that the problem is caused by either insufficient boost pressure or worn-out injectors, which leads to the issues described above. However, it is noticeable that pressure is building up, at least the rubber hoses on the EGR system are expanding. I'm not sure if that means anything.
What do you think about that?

My questions:

Can the technicians at VauWeh read the boost pressure using a diagnostic computer?
I have the two expensive Pierburg pressure regulators with the part numbers 1H0 906 627 and with the letter 'A' included.
Does anyone know the difference between versions with and without the 'A'? And can these be exchanged for the cheaper versions?
What do you think a diagnostic test will cost at a VAG or Bosch service center?

P.S. To solve the problem with the poor cold start, I once considered building a small electronic device that would simulate a cold engine for 2 seconds during startup. It would only require connecting a ~5kohm resistor to the sensor lead, and a timer would switch back to the actual engine temperature sensor after 2 seconds. The engine starts perfectly fine when the temperature sensor is disconnected, so it seems like a simple solution.

I would appreciate any help.

Um, have you ever considered 'Friend LMM'? Is that a good option?

According to my 'friendly' acquaintance, the Lmm (likely referring to a measurement or value) is within acceptable limits. However, a measurement test has not been performed.
The problems I described are only mildly noticeable and only become apparent in the higher load range (e.g., during overtaking maneuvers or when driving uphill with strong acceleration).
I forgot to mention that the power delivery is weak between 1500-2000 RPM, but then kicks in quite strongly around 2000 RPM.
All of this is accompanied by a dull rumbling sound, which, in my opinion, originates from the intake manifold.
Of course, the LMM (likely referring to a mass airflow meter) could also be faulty.

Hello,

Have you already checked the simplest things that could cause a loss of power, such as a clogged diesel filter or leaks in the diesel lines?
Are there any large air bubbles or foam visible in the hose between the diesel filter and the fuel injection pump when the engine is running?

Best regards, Rainer.

Of course, the Lmm could also have a problem.

Try this:
/viewtopic.php?t=954&highlight=diode+lmm

It worked wonders for me... Of course, it's always better to buy a new mass airflow sensor (MAF) if the car runs properly again after replacing the diode.

flightmaster wrote:

My suspicion is that the problem is caused by either insufficient boost pressure or worn-out injectors, which leads to the issues described above. However, it is noticeable that pressure is building up, at least the rubber hoses on the EGR system are expanding. I'm not sure if that means anything. What do you think about it??

Hi.

What do you mean by "soft nozzles"?

Which rubber hoses expand under what operating conditions? Are you referring to the thick suction hoses?

Power loss and poor warm-up also smell like a pump that is likely overdue for adjustment.
Was the ZR (water pump) recently replaced?

No, no... the diesel filter is okay, everything is sealed, no air leaks. I even blew through the return line, as it *could* be blocked.
I had to book an appointment with the 'friendly' mechanic today because I didn't have the necessary equipment.
When you get there... speechless. Then the mechanic tells me something about a lambda sensor. Crazy, right? I thought I misheard him. :twisted:
I immediately made a list of things that the guys there should check. Unfortunately, they don't like people looking over their shoulders.
The pump adjustment is set quite high. The timing belt was replaced 40,000 km ago, but I've also suspected a poorly adjusted pump in the past.
I meant by 'sluggish nozzle' a too-low injection pressure. Unfortunately, I don't have much experience with that. I haven't experienced any strong knocking or irregular idling.

Expanding rubber hose. I'm referring to the thick one (approximately 60mm in diameter) that runs from the coolant reservoir to the AGR valve.
When the vehicle is stationary and the accelerator is pressed, the turbocharger inflates due to the boost pressure. However, it also deflates once a certain engine speed is reached.

I've noticed that the vacuum sensor on the turbocharger is fully activated even when the engine is idling.
Is that how it's supposed to be?
I also have the 'Etzold' book, 'How it's done.' It shows the routing of the pneumatic control hoses for the EGR and turbocharger differently than how I have it installed.

What do you think about my idea for a temperature sensor for the engine?

flightmaster wrote:

Swollen rubber hose. I meant the thick one (~60mm) that runs from the LLK to the AGR. When the vehicle is stationary and the accelerator is pressed, the turbocharger inflates due to the boost pressure. However, it also deflates once a certain engine speed is reached. I've noticed that the vacuum sensor on the turbocharger is fully activated even when the engine is idling. Is that supposed to be like that?

Hi.

I can't identify any clear error indications here; it seems to be normal, as far as one can tell without specific pressure and speed values.

Quote:

What do you think about my idea for a temperature sensor for the engine?

For me, relying on sensor hacks is more like a hidden admission of defeat regarding the actual problem – a last-ditch effort to make something work, somehow.
Before that, I would check the pump settings and the values provided by the temperature sensor itself. Unfortunately, you need a VAGCOM or similar tool to do that.